Surgical stapler

ABSTRACT

A surgical stapler comprises a hollow shaft  10  and a tube  92  slidable axially within the shaft between a forward position wherein one end  96  of the tube projects beyond a free end of the shaft to enter a puncture site in a blood vessel and a rearward position wherein the end of the locator tube is retracted within the shaft. A surgical staple  40  straddles the tube  92  and is slidable thereon forwardly towards an anvil  24  against which the staple may be deformed to staple together the opposite edges of the puncture site. A cam mechanism drives the staple forwardly along the tube  92  into deforming engagement with the anvil and at the same time retracts the tube into the shaft in time to allow the legs of the staple to close onto the puncture site.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of application Ser. No.09/948,813, filed Sep. 7, 2001, entitled “Surgical Stapler,” whichclaims priority to Ireland Application No. S2000/0722, filed Sep. 8,2000 and Ireland Application No. S2000/0724, filed Sep. 8, 2000, each ofwhich are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to an instrument, herein called asurgical stapler, for closing a puncture in a liquid-carrying vessel byapplying a staple across the puncture so as to effect a closure. Theinvention relates particularly to surgical staplers for closingpunctures in blood vessels.

BACKGROUND TO THE INVENTION

[0003] When performing catheterisation procedures, such as angiographyor angioplasty, a catheter is generally introduced into the vascularsystem by first penetrating the skin, underlying tissues and bloodvessel with a sharpened hollow needle. Next, a guidewire is commonlyinserted through the lumen of the hollow needle and is caused to enterthe selected blood vessel. Subsequently the needle is typically strippedoff the guidewire and a combination of a dilator and/or introducer (oran introducer alone) are fed over the guidewire and pushed through theskin to enter the blood vessel. The guidewire can then be removed and adesired catheter to carry out the procedure is fed through the lumen ofthe introducer and advanced through the vascular system until theworking end of the catheter is appropriately positioned. Following theconclusion of the catheterisation procedure the working catheter will bewithdrawn and subsequently the dilator and/or introducer will also beremoved from the wound. Following this procedure the vessel puncturemust be closed in order to prevent loss of blood through the puncturehole.

[0004] Typically the wound is closed by maintaining external pressureover the vessel until the puncture naturally seals. This procedure cantake approximately 30 minutes with the length of time usually beinggreater if the patient is hypertensive or anticoagulated. The procedurecan also be uncomfortable for the patient and involves costlyprofessional time on the part of the hospital staff. Other pressuretechniques such as pressure bandages, sandbags or clamps have beenemployed but these also involve ensuring the patient remains motionlessfor an extended period of time and is monitored to ensure theeffectiveness of the procedure.

[0005] A number of devices have been developed in recent times whichprovide an obstruction in the area of the puncture in order to preventbleeding. For example, U.S. Pat. Nos. 4,852,568 and 4,890,612 disclose adevice which utilises a collagen plug which when placed at the bloodvessel opening absorbs body fluids, swells and affects a seal. Otherplug like devices, for example U.S. Pat. Nos. 5,222,974 and 5,282,827,describe a plug and anchor device, the anchor being positioned insidethe vessel and the collagen plug outside the vessel thereby sandwichingthe puncture between both and effecting a closure.

[0006] WO 98/17179 discloses a surgical stapler having a blood locatortube adjacent the stapling head. A guidewire passes through an openingat the end of the tube and up through a hollow bore in the tube, so thatthe stapler can be fed onto the guidewire and down onto the puncturesite. When the device reaches the puncture site, the tip of the tubeenters the blood flow within the artery and blood passes through thetube and out of the distal end at a point visible to the clinician. Theclinician can then actuate the stapling mechanism in the knowledge thatthe stapling head is at the puncture site in the arterial wall.

[0007] It is an object of the present invention to provide an instrumentfor closing a puncture in a liquid-carrying vessel by stapling.

SUMMARY OF THE INVENTION

[0008] According to the present invention there is provided a surgicalstapler comprising a shaft, a locator slidable axially of the shaftbetween a forward position wherein the locator projects beyond a freeend of the shaft to enter a puncture site in a liquid-carrying vessel ina human or animal, thereby to locate the free end of the shaft at thepuncture site, and a rearward position wherein the locator is retractedrelative to the shaft, a surgical staple straddling the locator andslidable forwardly thereon, said staple having forwardly pointing legsdisposed respectively on opposite sides of the locator, an anvil againstwhich the staple may be deformed to staple together opposite edges ofthe puncture site, and an actuator for driving the staple forwardlyalong the locator into deforming engagement with the anvil and forretracting the locator in coordination with the movement of the staplesuch that the locator is withdrawn from between the legs of the staplein time to allow the legs of the staple to staple together oppositeedges of the puncture site.

[0009] In another aspect the invention provides a method of staplingclosed a puncture site in a liquid-carrying vessel in a human or animalbody, comprising the steps of:

[0010] introducing a stapling mechanism to the location of the vessel;

[0011] positioning the stapling mechanism at the puncture site by meansof a locator associated with the stapling mechanism and projectingforwardly thereof, the locator sensing the position of the puncture siteby entering the vessel at the site;

[0012] delivering a staple to, and deforming the staple to close, thepuncture site; and

[0013] in co-ordination with the delivery and deformation of the staple,withdrawing the locator from the puncture site such that the locator isfully withdrawn from the vessel by the time the staple is fully deformedto close the puncture site.

[0014] Preferably, the steps of delivering and deforming the staple andin co-ordination therewith withdrawing the locator are effected byoperating a single control on a stapler actuating mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] An embodiment of the invention will now be described, by way ofexample, with reference to the accompanying drawings, in which:

[0016]FIG. 1 is a perspective view of an embodiment of a surgicalstapler according to the invention;

[0017]FIG. 1(A) is an enlarged perspective view of the free end of theshaft of the stapler of FIG. 1;

[0018]FIG. 2 is a perspective view of the stapler of FIG. 1 with theleft-hand side handle removed;

[0019]FIG. 3 is a perspective view of the stapler of FIG. 1 with theright-hand side handle and shaft removed;

[0020]FIG. 4 is an exploded perspective view of the components seen inFIG. 3 further omitting the left-hand side handle;

[0021]FIG. 5 is an exploded perspective view of the internal componentsat the free end of the shaft;

[0022]FIG. 6 is a perspective view of the internal components at thefree end of the shaft in the pre-fire position and omitting theleft-hand side of the shaft;

[0023]FIG. 7 is a side elevation of the components of FIG. 6 in thepre-fire position;

[0024]FIG. 8 is a front elevation of the components of FIG. 6 in thepre-fire position;

[0025]FIG. 9 is a perspective view of the internal components of thefree end, showing the position of the components in mid-cycle with fullyformed staple;

[0026]FIG. 10 is a side elevation of the components of FIG. 9 in thepost-fire position;

[0027]FIG. 11 is a perspective view of the blood locator tube withenlarged views of the front and rear portions, FIG. 11A and FIG. 11Brespectively;

[0028]FIG. 12 is a side sectional elevation of the front portion of analternative embodiment of the blood locator tube of the stapler;

[0029]FIG. 13 is a perspective view of the front portion of the bloodlocator tube shown in FIG. 12;

[0030]FIG. 13(A) is a perspective view of the front portion of analternative embodiment of the blood locator tube shown in FIG. 12;

[0031]FIG. 14(A) is a perspective view of the surgical staple in thepre-fire (pre-deformed) state;

[0032]FIG. 14(B) is a perspective view of the surgical staple in thepost-fire (deformed) state;

[0033]FIG. 15 is an enlarged perspective view of the cam mechanism;

[0034]FIG. 16 is a side elevation of the cam mechanism;

[0035]FIG. 17 is a side elevation of the shaft section of the device andsuction port; and

[0036]FIG. 18 is an end view of the surgical staple, locator tube andinsert.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Referring to the drawings, the stapler comprises a rigid shaft 10extending from a moulded plastic housing 12 shaped in the form of apistol-like handle. The shaft 10, which is hollow to accommodate variousmoving components to be described, comprises right and lefthand sides10A, 10B respectively which are secured together at the distal free endby a section of heat shrinkable tubing 91 in combination withinterference pins and mating cavities 15A and 15B (FIGS. 4 and 5) alongthe edges of the distal tip, and at the proximal end by pins 17A matingin an interference fit with corresponding cavities 17B (FIGS. 2 and 3)captured within the housing 12. Likewise, the housing 12 comprises leftand right-hand sides 12A, 12B respectively.

[0038] The major part of the exposed length of the shaft 10 has aconstant circular cross-section, but at its free end the shaft 10 has aportion 14 of increased diameter having a “bullet” profile. One end ofthis bullet portion 14 is tapered down toward a staple exit slot 16while the other end is tapered down to the remaining section of theshaft, which extends back into the housing 12. The ratio of the maximumdiameter of the bullet portion 14 to the diameter of the remainingsection of exposed shaft is approximately 5:4. Heat shrink sleeve 91sits flush with the surface of the bullet portion 14, to ensureatraumatic entry, percutaneously, into the tissue.

[0039] The reason for the bullet profile is so that the shaft 10 is asatraumatic as possible during introduction to the body to minimise theamount of force and tissue dilation required when tracking the devicepercutaneously over a guidewire 18 and onto the surface of a bloodvessel adjacent a puncture hole, as will be described. In an alternativeembodiment, not shown, the bullet portion 14 is oval in cross-sectionwith the major axis of the oval being coincident with the staple exitslot 16, so as to minimise the circumferential length for a given staplewidth.

[0040] The bullet portion 14 of the shaft 10 houses a staple 40 and astaple delivery mechanism (FIGS. 4 to 7). The staple delivery mechanismcomprises a tiltable anvil 24 and a pair of rod-like actuating members,namely an elongated anvil support 30 and an elongated staple former 52,the latter being slidable in the shaft 10 and operated by atrigger-operated cam mechanism 62 in the handle housing 12.

[0041] The anvil 24 has a pair of upstanding fingers 24A at the frontand a pair of downwardly inclined tilt arms 24B at the rear. The anvil24 is tiltably mounted in the bullet portion 14 by a pair of wings 26which are pivotable in recesses 28 in the right-hand side 10A of theshaft 10 (the wings 26 are retained in the recesses by the underside ofprojections 54 on the former 52).

[0042] Tilting of the anvil 24 is effected by the cam mechanism 62 viathe anvil support 30, which is slidable axially within the right-handshaft side 10A in channel 32. The front end of the anvil support 30 isbifurcated to form two arms 34 having lateral projections 36 (FIGS. 6and 7). The arms slide in rebates 38 in the right-hand shaft side 10A.The anvil support 30 is movable, by the cam mechanism 62, from a forwardposition, FIGS. 6 and 7, wherein the arms 34 extend under the anvil'ssupport wings 25 to support the anvil forming fingers 24A directly infront of a surgical staple 40 to be delivered, to a rearward position,FIG. 10, wherein the arms 34 are withdrawn under the downwardly inclinedtilt arms 24B at the rear of the anvil 24 so as to tilt the anvilanti-clockwise (as seen in FIG. 10) and displace the fingers 24A out ofthe path of the staple 40. The angle of incline of tilt arms 24B may beincreased to cause separation of the two shaft halves, in addition todisplacing the fingers 24A out of the path of the formed staple, to aidin staple release. This is achieved by the anvil (in its fully tiltedposition) applying pressure to the underside of former 52 and the uppersurface of the right shaft 10A.

[0043] Referring additionally to FIGS. 11, 11A and 11B, a hollow bloodlocator tube 92 is slidable axially within the shaft 10 in a channel 44in the anvil support 30 and in an opposing U-shaped channel 53 in thestaple former 52. The tube 92 extends the full length of the shaft 10and has a constant, generally oval or elongated cross-section, except atits distal tip 14 where the locator tube 92 is formed into a narrowopening 96 and at a crimped region 94 towards the rear of the tube 92which is formed to allow only the guidewire 18 and not blood to exit therear of the locator tube.

[0044] Under the action of the cam mechanism 62 the tube 92 is slidableaxially in the shaft 10 between a forward position, FIGS. 6 and 7,wherein its front end projects beyond the bullet portion 14 of the shaft10 under the influence of a leaf spring 88 to be described, and arearward position, FIGS. 9 and 10, wherein the front end of the tube 92is retracted within the bullet portion 14 behind the fingers 24A of theanvil 24 during the rotation of cam 62.

[0045] The purpose of the blood locator tube 92 is to follow apreviously placed guidewire 18 to a puncture site in a blood vessel,thereby to locate the free end of bullet portion 14 of the shaft 10against the exterior wall of the blood vessel at the puncture site. Toproperly locate the bullet portion 14 the front end of the tube 92 mustactually penetrate the blood vessel wall at the puncture site and thisis indicated by blood flowing back through the tube 92 and out through ablood outlet port 93 (FIG. 11) in the tube. A channel (not shown) in thepart of the left-hand side 10B of the shaft 10 within the housing 12provides communication between the port 93 and a blood exit port 50(FIG. 1) on the side of the housing 12B, so that the blood flowing backthrough the tube 92 is visible at the exterior of the housing.

[0046] A blood exit port adapter 51 (FIG. 1) may be secured into theopening of the blood exit port 50 via a matching male luer taper 51A toenhance the visibility of the exiting blood. The blood exit port adapterhas a reduced internal diameter, relative to the opening of the bloodexit port 50, which for a constant blood flow increases the pressure ofexiting blood causing a jet effect of exiting blood.

[0047] In the absence of the blood exit port adapter, the blood exitport's female luer taper opening matches that of the standard medicalsyringe's male luer taper making it possible at any time during thedevice's use to inject fluid via the blood exit port into the lumen ofthe locator tube to exit at its distal tip. This may be necessary fromtime to time to clear the locator tube's lumen of congealed blood and oftrapped soft tissue. Alternatively, radiopaque contrast medium may beinjected via the locator tube to confirm the relative location of thelocator tube's distal tip to that of the blood vessel wall byfluoroscopy, or any injectable fluids may be injected for diagnostic ortherapeutic reasons.

[0048] The blood outlet port 93 is sized to have a minimum areacorresponding to the available blood entry area at the distal tip;however, is narrower (in a transverse aspect) than the diameter of theguidewire 18 to prevent the guidewire inadvertently exiting the bloodoutlet port during insertion, instead of exiting from the intendedproximal end of the locator tube.

[0049] It has been found that the naturally formed shape of puncturewounds in arterial walls is elongated rather than round. Whereas thehole is formed by introducing instruments generally of round crosssection, the wall tends to open generally along a transverse line whichlies in the direction of the circumference of the artery (rather thanalong the axis of the artery). By having a generally oval blood locatortube, the locator tube (when introduced by the clinician with the majoraxis of the oval perpendicular to the axis of the artery), will fit morenaturally within the arterial opening. The consequence of this is thatthe wound edges which are to be stapled together, lie closer togetherthan if a tube of circular cross section were to be used.

[0050] This in turn has the consequence that the staple used need not beso large, and in turn, the dimensions of the shaft, which mustaccommodate the staple when in its unformed state, can be reduced,leading to less trauma for the tissue into and from which the shaft isintroduced.

[0051] A further consequence of having a generally oval or elongatedcross section for the locator tube is that the tube will be moredisposed to the centre of the puncture than with a rounded tube. Thepresent embodiment has a staple which straddles the locator tube,thereby increasing the likelihood of the staple closing the elongatedwound at its centre rather than towards one or other of the extremitiesof the wound.

[0052] The opening 96 at the front of the tube 92 has an approximatelycircular portion 96A at the extreme forward tip of the tube which is ofgreater diameter than the width of the remaining portion 96B of theopening 96. The portion 96B is in the form of a slot which is alignedwith the major axis of the elongated cross-section of the tube 92 andslopes rearwardly from the circular portion 96A. The guidewire 18, whichpasses through the tube 92, FIG. 11, is chosen to be of sufficientlysmaller diameter than the diameter of the opening 96A at the front endof the tube 92 for the guidewire 18 to be easily inserted into the tube92 and pass through the opening 96A. However, the guidewire is alsochosen to be too large to fit within the remainder 96B of the opening96. In this way guidewire 18 is constrained to remain in opening 96A,and the size of opening 96A sets an upper limit on the diameter ofguidewire which can be used with the device. One could introduce anarrow neck or constriction into the opening 96 just above opening 96A(at the points indicated by 96C) to ensure that very small guidewireswere constrained within the enlarged opening 96A, but in general this isunnecessary as the guidewire will normally be supplied with the device,or the device will only be supplied for use with a particular gauge ofguidewire.

[0053] The rear crimp 94 and tip opening 96A are positioned to encouragethe guidewire to lie along the bottom curved surface of the tube, i.e.that portion of the tube lying in a direct line between the opening inthe crimped end and the opening 96A. This helps prevent guidewire 18from laying up against the inside of blood exit port 93 and preventingegress of blood, FIGS. 11A and 11B.

[0054] The curvilinear nature of opening 96 increases the availableinlet area to match that of the available area within the body of thelocator tube with the guidewire 18 in situ.

[0055] The slot-like opening 96B slopes away from the circular opening96A for ease of insertion into the vessel opening and to reduce thepotential of trauma to the inner wall of the vessel opposite the openingbeing stapled. This is achieved because the guidewire 18 protruding fromopening 96A will tend to push the opposite wall of the vessel away fromthe locator tube tip, and the point at which the guidewire protrudes(due to it being constrained in the opening 96A) is the farthest partforward of the tip. Thus, the shape of the tip is streamlined away fromopening 96A to prevent any part of the tip gouging into or otherwisedamaging the inner vessel walls. Also, the peripheral edges 95 of theopening 96 are bent inwardly to as to avoid sharp edges which mightdamage soft tissue and the vessel wall.

[0056] The distal end of an alternative embodiment of a locator tube 42is shown in FIGS. 12 and 13. This embodiment also has a substantiallyconstant elongated cross-section, which in this case converges to anapproximately circular guidewire opening 46 at the extreme forward tipof the tube. The guidewire 18, which passes through the tube 42, isusually chosen to be of sufficiently smaller diameter than the diameterof the opening 46 for there to be an adequate gap for the blood to passback through the tube 42 even in the presence of the guidewire. However,further openings 46A are provided in opposite sides of the tube 42 justbehind the front opening 46 to allow more ready access of the blood tothe interior of the tube in cases where the guidewire 18 may not leave alarge enough gap for passage of blood solely through the opening 46. Thethree openings 46, 46A, 46A in fact form respective portions of a singlefront opening, being in reality three connected lobes, all connected byconstricted channels 47, and all in communication with the interior ofthe tube.

[0057] An alternative embodiment is shown in FIG. 13(A) where the threeopenings 46, 46A and 46A, while collectively constituting the frontopening of the tube 42, are independent of each other. Again, opening 46at the front of the tube is sized to receive a maximum size of guidewireand openings 46A are sized to allow a sufficient flow of blood to enterthe locator tube.

[0058] A problem can arise in devices of this type where an oversizedguidewire is used which occludes the hollow interior of the bloodlocator tube and thereby prevents blood flow back through the tube. Toprevent this situation the lobe 46 through which the guidewire emergesin the tip of the tube of FIGS. 12, 13 and 13A is of a lesser diameterthan the internal bore of the tube. The dimensions of this lobe 46 set amaximum for the guidewire diameter for use with the device, and ensurethat even when this maximum diameter guidewire is used, there is stillsufficient internal clearance within the tube bore to allow a strongblood flow through the tube from the other lobes 46A.

[0059] The staple 40 straddles the blood locator tube 92 within thebullet portion 14 of the shaft 10, see FIGS. 6 and 8, and is slidablethereon forwardly towards the free end of the bullet portion 14. Inparticular (see also the enlarged view of FIG. 14), the staple 40comprises a back or base portion 40A from which extend perpendicularlyat each end respective legs 40B which terminate in sharpened points. Thebase portion 40A and legs 40B lie in substantially a common plane exceptfor a centre portion 40C of the base portion 40A which is deformed in adirection perpendicular to the legs 40B so as to have an Ω (omega) shapegenerally complementary to the external cross-sectional profile of theblood locator tube 92 and internal cross-section of an insert 160, to bedescribed. The base section 40A is pre-bent to between 150° and 170° atpoints A and B equidistant from the centre of the base, positioned tomaximise the closure of the closed staple (and is relevant to the depthof forming wings 54 on the former 52). The base section is also deformedat points C & D so as to narrow the cross sectional width of the wire atboth points thereby directing the staple to bend at these points. Thestaple 40 is mounted on the blood locator tube 92 such that the centreportion 40C of the staple sits on the upper half of the tube 92, as seenin FIGS. 6 and 8, where the narrow open section of the omega shape isapproximately equal to the width of the tube and with the legs 40Bpointing forwardly on opposite sides of the tube 92. The depth of thecentre portion 40C of the staple 40 is such that the legs 40B of thestaple lie substantially directly on opposite sides of the central axisof the tube 92. This will ensure that the staple 40 is positionedcentrally across the puncture hole in the blood vessel. In order toavoid the guidewire 18 fouling the staple 40 when the latter is closedon the puncture site, the hole 96A is offset below the plane containingthe legs 40B of the staple, FIG. 8.

[0060] The metal insert 160 is received in a recess in the left-handshaft side 10B within the bullet section 14. The insert 160 providesmechanical support for the omega section 40C of the staple 40 during thestaple forming process and is engaged by the former 52 during the stapleejection phase of the process so as to separate both halves of thebullet section for easy staple release. The insert is profiled togenerally correspond with the external profile of the omega shapedportion 40C of the staple. At the distal end the insert profile tapersdown to closely approximate the omega-shaped portion of the staple 40C(FIG. 18). This has the effect of offering mechanical support to theomega-shaped portion of the staple during the staple forming process,during which the base section is bent about the anvil fingers. Thisbending motion in turn causes the omega to open up or flatten out. Themetal insert prevents this from happening only allowing the staple baseto deform around the anvil. The omega interlock system between thestaple 40 and insert 160 (FIG. 18) also stabilises the staple,vertically, within the staple exit plain during the forming process,whilst allowing easy staple release once formed, due to the relativelysmall contact area between staple and insert.

[0061] The staple former 52 has a cross-section conforming to that ofthe blood locator tube 92 and is slidable on the blood locator tube 92axially within the shaft 10. The former 52 is located behind the staple40 on the tube 92 and is operated by the cam mechanism 62. At its frontend the former 52 has a pair of forming arms 54 which are so shapedthat, when the former 52 is driven forward by the cam mechanism 62, thestaple 40 is driven against and deformed around the anvil fingers 24A sothat the legs 40B of the staple close together (FIG. 9) onto thepuncture site. The surface of the forming arms which contact the staple55 may be so profiled to match the cross-sectional geometry of thestaple. This matching profile stabilises the staple on the formingsurfaces of the forming arms 54 during the high pressure contact withthe staple during staple forming and closure. During the forwardmovement of the staple, the staple legs slide toward the anvil 24 alonga track defined by the staple exit slot 16 between the opposite halvesthe bullet portion 14. The slot 16 provides a slight interference fit onthe staple legs 40B to prevent the staple 40 moving forward duringstorage of the device or prior to firing. The slot 16 further preventsthe staple rotating in the horizontal plane (FIGS. 7 and 10) during itsforward travel. Once forming of the staple around the anvil is completedthe forming force is removed from the former 52 by a drop-off in thecam, the anvil is lowered and the former advanced again to eject thestaple from the device. During this forward movement (ejection phase),the sloped edges 52A and 52B of the former engage with the metal insert160 to prise open the bullet section of the shaft assembly thusfacilitating staple release.

[0062] The cam mechanism 62 can be seen in FIG. 3 and in enlarged viewsof FIGS. 15 and 16. The mechanism 62 consists of a first cam 58 and asecond cam 60 mounted on a common axis 62 which sits in a recess 64 inthe left-hand side 10A of the shaft (FIG. 4) and a corresponding recess(not shown) in the right-hand side 10B. Trigger 56 is similarly mountedin the shaft by a pair of stub axles 66 which are received in a triggerseating recess 68 in each half of the shaft 10, FIG. 4.

[0063] An actuating pin 70 extends through the first and second cams 58,60. This actuating pin is acted on by a cam actuating surface 72 (FIG.3) provided on the trigger 56, so that when the trigger is squeezed theactuating surface moves the actuating pin in an anticlockwise directionaround the axis 62. Because the actuating pin extends through both cams58, 60 of the mechanism 62, the cams are both rotated simultaneouslythrough the same angle as determined by the trigger squeeze. The use ofthis cam mechanism ensures accurate timing and positive mechanicaldisplacements of all the moving components and accurate movement of thecomponents relative to each other. The geometry of the trigger pivotpins 66 and actuating surface 72 relative to the cam pivot 62 and camactuating pin 70 is configured to minimise the trigger rotation to only23 degrees whilst the cam rotates a total of 90 degrees. Thisconfiguration also provides a mechanical advantage that the triggerdelivers to the cam-actuating pin 70 of approximately 1:4. This geometryis further configured to deliver the best mechanical advantage at thephase during the staple forming cycle, which requires the highestforming forces, having the advantage of minimising the trigger effortand ensuring a constant trigger effort over the full cycle. Trigger 56further comprises a ratchet lever 73B, shown in FIG. 3, which engageswith ratchet strip 73A, which is mounted in the right handle 12A, FIG.3. This non-return ratchet system ensures the firing cycle of the stapleis uninterrupted, non-repeatable and provides a positive indication thatthe device has been used.

[0064] Referring back to FIG. 3, a leaf spring 88 positioned in a recessin the left-hand side 10A of the shaft and a corresponding recess (notshown) in the right-hand side 10B. The free ends of the spring areformed into a loop so as to pivot freely in the curved corner recessesin which it sits and to aid assembly. The apex of this spring ispositioned in a slot 74 in the crimped portion 94 of the blood locatortube 92 thus assuming the role of cam follower for the blood locatortube. This blood locator tube cam follower 74 is acted on by the firstcam 58. Similarly, the first cam 58 acts on a former cam follower 76,whereas the second cam 60 acts on anvil-support cam followers 78A and78B. The shape of the first and second cams 58, 60 are shown inelevation in FIG. 16 (the second cam 60 is shown in dotted outline as itis concealed by the first cam). FIG. 16 also shows actuating pin 70, anda reinforcing strut 80 mounted between the first and second camsdiametrically opposite the actuating pin 70.

[0065] The cams are shown in the starting positions in FIGS. 15 and 16.Squeezing the trigger fully (through an angle of 23 degrees) causes thecams to rotate anticlockwise through 90 degrees.

[0066] The apex of the leaf spring 88 which engages with and operates asa cam follower for the blood locator tube (leaf spring apex) actsagainst the rear surface 82 of the first cam 58. As the first camrotates anticlockwise from the position shown in FIG. 15, the distancebetween the blood locator tube cam follower 74 and the axis 62 isincreased. This causes the blood locator tube to be drawn backwards asthe trigger is squeezed.

[0067] The former cam follower 76 acts against the front surface 84 ofthe first cam 58. Again the distance between former cam follower 76 andaxis 62 increases through the initial stages of the trigger beingsqueezed. The profile of surface 84 is designed with two distinctnon-linear efficiencies, transitioned from low mechanicalefficiency/high displacement to high mechanical efficiency/lowdisplacement. The first rise rate being for displacement of the staplefrom its starting position to initial forming against the anvil, whichrequires the largest displacement of the staple with minimal load. Thesecond non-linear rise rate is designed to correlate the cams mechanicalefficiency with the load profile required to form the closed staple,minimising the trigger effort required and ensuring a constant triggereffort over the full cycle. A V-shaped section 84A of front section 84causes the former 52 to momentarily suspend its forward motion when thestaple has been fully formed. The effect of this is to momentarilyrelease the pressure off the formed staple against the anvil, allowingthe anvil to be dropped. The geometry of the distal tip of the former isdesigned to provide sufficient intrinsic spring tension to allow theforming arms 54 to further squeeze the formed staple, once the anvil hasdropped, to further closed the formed staple. As the cam continues torotate the raised profile 84B on the cam causes the former to advanceforward again, ejecting the staple clear of the device.

[0068] It can be seen that a raised hump 82A on the profile of the rearsurface 82 of the first cam is located almost diametrically opposite theV-shaped section 84A. The reason for this is to increase the rate atwhich the blood locator tube is drawn out of the puncture site justbefore the staple is fully formed and released. The intention is toleave the tube in the puncture as late as possible to provide supportfor the walls of the blood vessel for as long as possible And also toensure that the head of the device remains centred over the puncturehole. The blood locator tube 92 is biased forward by the blood locatortube leaf spring 88 which also maintains pressure between the apex ofthe spring and the rear surface 82 of the first cam 58.

[0069] The blood locator tube leaf spring 88 allows the locator tube tobe displaced in a proximal direction (back into the shaft of the device)against the spring tension in the event that the locator tube meets anysignificant resistance during insertion of the device, to preventunnecessary trauma to soft tissues, the vessel or its rear wall.

[0070] An example of where this is particularly useful is if the stapleris advanced too far into the vessel, so that the tip of the tube 92meets the inner wall. The blood locator tube will then be displaced backinto the shaft, and may be designed to protrude through the end of thehandle housing to give a visual indication that the device has beeninserted against the wall. Furthermore, the device may be designed sothat the blood outlet port 93 on the tube 92 is brought out of registrywith the blood exit port 50 in the handle housing when the tube isdisplaced backwards, so that the clinician will note the flow of bloodceasing when the tube meets the inner vessel wall in this way.

[0071] The cam mechanism 62, however, provides positive mechanicaldisplacements for withdrawing the locator tube at the appropriatetiming, to ensure there is no chance of the staple being formed whilstthe locator tube is in a forward position and potentially interferingwith the staple formation.

[0072] A further reason to leave the blood locator tube in the puncturehole as late as possible is that the continued retraction of the tubeeverts or turns outwards the opposed edges of the puncture wound andaids penetration of the staple legs into the arterial wall. Eversion ofthe edges of the puncture helps prevent thrombus formation within thevessel. Yet another reason to leave the blood locator tube in thepuncture hole as late as possible is to ensure that the stapler headremains centred over the hole during the staple delivery process. Whenthe locator tube is fully retracted, only the guidewire is left withinthe wound, and this will be easily retracted from the closed wound afterthe stapler has been removed from the puncture site.

[0073] The anvil-support cam follower 78B acts against the rear surface90 of the second cam 60. It can be seen that this rear surface 90provides the greatest increase in distance relative to the axis to thesection 90A from about 60 to 90 degrees below the horizontal. The reasonfor this is that the anvil is maintained in place until the staple hasbeen formed and the pressure on the former has been relaxed slightly toallow the anvil to drop. The anvil is maintained in place for theinitial 60 degrees of rotation by the anvil-support cam follower 78Abeing in contact with cam surface 98 of cam 60, preventing theanvil-support 30 from moving from its starting position. The cam surface98 for the first 60 degrees of cam rotation is at a constant distancefrom the cam axle 62 (in dwell).

[0074] In use, the stapler is initially in the “pre-fire” configurationshown in FIGS. 6 to 8. The front end of the blood locator tube 92 is ina fully forward position projecting beyond the free end of the bulletportion 14 of the shaft 10, the anvil-support 30 is in a fully forwardposition with its arms 36 extending under the anvil's support wings 25ensuring the anvil fingers 24A are directly in front of the staple 40,the former 52 is in a fully retracted position away from the anvilfingers 24A, and the staple 40 is in its fully back position up againstthe forming arms 54.

[0075] In this configuration the external end of a previously positionedguidewire 18 is inserted into the hole 96A in the front end of the bloodlocator tube 92 and fed through the tube 92 until it exits a guidewireexit port at the rear of the housing 12. The stapler is now fed alongthe guidewire 18 until the tip 95 of the tube 92 enters the blood vessellumen through the vessel's puncture hole. This is indicated by bloodflowing out of the blood exit port 50 or, if present, the adapter 51. Atthis point the front end of the bullet portion 14 of the shaft 10 willbe resting against the exterior wall of the blood vessel.

[0076] Now the trigger 56 is squeezed, causing the cams of the cammechanism 62 to rotate through 90 degrees. As mentioned, the rear end ofeach of the blood locator tube 92, anvil-support 30 and former 52 arecoupled to the cam mechanism via cam followers and the followingcoordinated movement of these components takes place as the cams rotatethrough 90 degrees. (A).

[0077] 0 degrees: Stapler in pre-fire configuration.

[0078] 32 degrees: Former 52 forward sufficiently to clamp stapleagainst anvil fingers 24A, blood locator tube begins to retract. At thispoint the staple legs will have punctured the wall of blood vessel, butthe staple is not yet fully deformed.

[0079] 50 degrees: Former 52 forward sufficiently to deform the staplelegs around the anvil fingers 24A and close the staple on the puncturesite: blood locator tube 42 fully retracted. At some point between 32and 50 degrees, the blood locator tube will have withdrawn from betweenthe staple legs in time to allow them to close. This should be left aslate as possible to provide support for the walls of the blood vesselfor as long as possible.

[0080] 65 degrees: Clamp force released from staple (due to drop off incam profile). Anvil support 30 starting to retract.

[0081] 75 degrees: Anvil support 30 retracted sufficiently to actagainst anvil sloped tilt arms 24B. Anvil fingers 24A begin to drop.

[0082] 83 degrees: Anvil support 30 fully retracted. Anvil fingers 24Adropped down to allow release of staple. Intrinsic tension in formerarms 54 further closes the staple. Former 52 begins to move forwardagain to eject staple. Former 52 begins to interfere with the insert 160to spread bullet portion 14 of the shaft to allow for clear staplerelease.

[0083] 90 degrees: Former 52 fully forward; staple ejected from thedevice.

[0084] The use of cams in cam mechanism 62 ensures the accuracy ofsequence and relative timing between events as well as ensuring positivemechanical displacements of all components.

[0085] In a further embodiment to the above described device, on thecompletion of the cycle described above, further rotation of the camcauses the anvil support 30 to return to its fully forward position,lifting the anvil fingers 24A to their raised position behind the formedstaple being held in forming arms 54. The former is then retracted in aproximal direction (back into the shaft) causing the rear of the closedstaple to crash into the raised anvil fingers 24A, to be positivelyejected from within the forming arms 54 and the device. The additionalmovements of the anvil support and former may be facilitated byadditional cam lobes on cam 58; or alternatively spring driven, assistedand timed by appropriately positioned radial slots in cam 58 to allowingthe cam follower of the anvil support to move forward and the camfollower of the former to move rearwards.

[0086] In a further embodiment the trigger activates an automatic firingcycle, not shown. A tension spring attached to the cams is released fromits extended state so as to rotate the actuation cam through a 90 degreearc causing the same component movements as described above.

[0087] In an alternative embodiment, not shown, once the staple has beenformed the forward end of the former 52 retracts and engages pull armson the anvil-support 30 causing it to move in a rearward direction. Asit does so, it engages with the rear end of the anvil 24, which isangled downward into the path of the moving slide. Centrally opposedwings extend from the anvil and are located so as to pivot in opposedwing slots formed in the right-hand side 10A of the shaft. Once engagedwith the slide the rear end of the anvil is pushed upward causing it topivot about the wings and arc the forward end of the anvil downward. Asit does so, it disengages from the staple so that the device can beremoved from the puncture tract along the guidewire.

[0088] In a further embodiment the reverse profile 82 on the first cam58 which engages with the cam follower 74 on the blood locator tube 92is extended so that when the staple forming cycle is completed the firstcam continues to rotate causing the blood locator tube to move furtherin a proximal direction. At its distal end the blood locator tube haswings which as it moves in a proximal direction engages with the pullarms of the anvil-support 30 causing it to move in a proximal directionand engage the anvil tilt arms thereby disengaging the distal end of theanvil from the formed staple. In this embodiment the second cam isredundant and can be omitted.

[0089] In a further embodiment, FIG. 17, the bullet head 14 of the shaft10, which approximates the blood vessel wall 208, includes a number ofsuction ports 200. These ports are in communication with a suctionadapter 202 via capillaries 204 within the shaft section. Suction, froma standard wall suction outlet or independent suction pump, is suppliedto the suction adapter 202 via an on/off tap 206. Once the device is inposition on the arterial wall, as indicated by blood flowing from theblood exit port, the tap 206 is turned to the “on” position therebydelivering suction to the ports 200 on the bullet head 14. This in turnsuctions the blood vessel wall 208 against the face of the head 14 so asto stabilise it during delivery of the staple. Once delivered thesuction is deactivated so as to remove the device from the blood vesselwall and tissue tract.

[0090] The invention is not limited to the embodiments described hereinand may be modified or varied without departing from the scope of theinvention.

What is claimed is:
 1. A surgical stapler comprising a shaft, a locatorslidable axially of the shaft between a forward position wherein thelocator projects beyond a free end of the shaft to enter a puncture sitein a liquid-carrying vessel in a human or animal, thereby to locate thefree end of the shaft at the puncture site, and a rearward positionwherein the locator is retracted relative to the shaft, a surgicalstaple straddling the locator and slidable forwardly thereon, saidstaple having forwardly pointing legs disposed respectively on oppositesides of the locator, an anvil against which the staple may be deformedto staple together opposite edges of the puncture site, and an actuatorfor driving the staple forwardly along the locator into deformingengagement with the anvil and for retracting the locator inco-ordination with the movement of the staple such that the locator iswithdrawn from between the legs of the staple in time to allow the legsof the staple to staple together opposite edges of the puncture site. 2.The surgical stapler of claim 1, wherein the actuator drives the staplevia an elongated former slidable axially of the shaft.
 3. The surgicalstapler of claim 2, wherein the anvil is tiltable relative to the shaftaxis between a first position wherein the anvil is in a position forengagement by the staple and a second position wherein the anvil isclear of the staple, the actuator further including a tilting mechanismfor tilting the anvil in co-ordination with the movement of the locatorand staple such that the anvil is tilted from the first position to thesecond position after closure of the staple onto the puncture site. 4.The surgical stapler of claim 3, wherein the tilting mechanism fortilting the anvil comprises an elongated member slidable axially withinthe shaft.
 5. The surgical stapler of claim 3, wherein the locator has agenerally oval cross-section.
 6. The surgical stapler of claim 3,wherein the forward end of the locator is tapered.
 7. The surgicalstapler of claim 3, wherein the legs of the staple lie substantiallydirectly on opposite sides of a central axis of the locator.
 8. Thesurgical stapler of claim 3, wherein the locator comprises a hollow tubehaving an opening at the forward end to enable liquid flow to be sensedwithin a liquid-carrying vessel to thereby locate the puncture site inthe vessel.
 9. The surgical stapler of claim 8, wherein a guidewire iscarried within the locator tube and wherein said guidewire emerges fromsaid tube at the opening.
 10. The surgical stapler of claim 9, whereinthe opening at the forward end of the locator tube is disposed on thetube so as to cause the guidewire to emerge offset from between the legsof the staple.
 11. The surgical stapler of claim 10, wherein a portionof the shaft has an increased diameter at its free end.
 12. The surgicalstapler of claim 10, wherein the shaft is attached to a handle and theactuator comprises a cam mechanism mounted in the handle.
 13. Thesurgical stapler of claim 12, wherein the cam mechanism comprises a camwhich drives the former forward to deform the staple against the anvil,and which is shaped to relax the driving force once the staple has beenformed to thereby enable the staple to be cleared from the anvil. 14.The surgical stapler of claim 13, wherein the cam mechanism is triggeroperated.
 15. A method of stapling closed a puncture site in aliquid-carrying vessel in a human or animal body, comprising the stepsof: introducing a stapling mechanism to the location of the vessel;positioning the stapling mechanism at the puncture site by means of alocator associated with the stapling mechanism and projecting forwardlythereof, the locator sensing the position of the puncture site byentering the vessel at the site; delivering a staple to, and deformingthe staple to close, the puncture site; and in co-ordination with thedelivery and deformation of the staple, withdrawing the locator from thepuncture site such that the locator is fully withdrawn from the vesselby the time the staple is fully deformed to close the puncture site. 16.The method of claim 15, wherein the steps of delivering and deformingthe staple and in co-ordination therewith withdrawing the locator areeffected by operating a single control on a stapler actuating mechanism.